1. Field of the Invention
The present invention relates to a rotor having permanent magnets and mechanism for cooling the same. More particularly, the invention relates to a rotor having a plurality of permanent magnets embedded in adjacent to a field core of the rotor for, e.g., a power generator, and a construction for cooling such a rotor.
2. Prior Art
A rotor has been known, e.g., from Japanese Patent Laid-Open No. 8-107639, which comprises providing spaces for embedding permanent magnets at the position in adjacent to the outer circumference, laminating field core pieces, and embedding the permanent magnets. However, such a rotor having gaps provided cannot sufficiently prevent the leakage of the magnetic flux of magnetic circuit. Due to the radiation heat from the armature, which increases the temperatures of the field core and/or permanent magnets embedded into the field core and due to insufficient cooling of the permanent magnets, sufficient output cannot be obtained in the case of the rotor having a large output. In such a rotor, with the operation of the power generator, the field core is heated by the radiation heat from the armature, such an increase in the temperature of permanent magnets also decrease in output of the power generator.
In the case of embedding permanent magnets in to field core in such a conventional rotor, the whole size of rotor becomes large, the magnet flux is frequently leaked and, thus, the output of the power generator is decreased. Furthermore, due to the radiation from the armature, the temperatures of the field core and the permanent magnet embedded therein are increased. Due to insufficient cooling of the field core and, in particular of the permanent magnet, the decrease in the output due to the heat cannot be avoided
Moreover, such a rotor also is disadvantageous in that the cooling air within the field core insufficiently flows, leading to a reduced cooling efficiency and, thus, increase in the output of the power generator cannot be expected.
As shown in FIGS. 19A and 19B, we have developed a lamination of the armature core for a rotating field core type power generator and filed as Japanese Patent Application No. 9-269046. The lamination construction of an armature sheets according to this application is a lamination (D.sub.1 -D.sub.n) of the armature sheets G in which the armature core sheets has a circular shape in order to store a field core of the power generator within the armature, which can revolves within the armature core, each armature is formed by punching plurality of V-shaped or trapezoid caulking portions K on the outer circumference, characterized in that V-shape or trapezoid caulking portions K are formed by punching the portions in adjacent to the teeth portions B projected on the inner circumference of the armature core D residing on the radial line from the axis O of the field core, and at the same time, when the armature sheets D are laminated to be a laminate construction (D.sub.1 -D.sub.n), said caulking portions K are fitted to tightly communicate the armature sheets D. (1) When the field core revolves at high speed within the armature, the teeth portions have an influence upon magnetic flux which frequently changes, resulting in vibration. The vibration due to the influence of the magnetic flux causes the magnetic route formed on the teeth portions to be irregular. Since V-shape or trapezoid caulking portions K are formed by punching the portions in adjacent to the teeth portions B, the loss of the magnetism caused by the irregular magnetic route can be prevented. Consequently, (2) uncomfortable feeling can be avoided and, at the same time, noise can be reduced. (2) When the length of the caulking portions K are punched along the radial line not shown from the axis of the field core, the magnetic route becomes uniform. Consequently, the loss of the magnetism can be prevented.